A general stability analysis method for regenerative oscillating heat engines based on heat-dynamics network model and Nyquist criterion

Regenerative oscillating heat engines (ROHEs), such as Stirling and thermoacoustic heat engines, are self-excited oscillating heat engines. In the design and application of these ROHEs, operating stability is of utmost importance. However, general and efficient stability analysis methods for ROHEs are still lacking. The present research focuses on developing a unifying approach for analyzing the stability of ROHEs through heat-dynamics network model and the Nyquist criterion. First, the general heat-dynamics network model as an analytical tool is provided for three typical ROHEs, including the travelling-wave, standing-wave thermoacoustic engine and Stirling engine. Then, based on the features of established network models, these ROHEs are regarded as either feedback or negative-resistance type oscillators, and their startup and stability characteristics are analyzed by combining the Nyquist criterion and PSO method so that the startup information and the limit cycle for these ROHEs are accurately obtained. In the meanwhile, the Nyquist criterion is extended to consider nonlinear effects in this paper. The prototype analyses show that the calculated results for the startup information and the limit cycle are in good agreement with those of the experiment or the related analysis, with a maximum error of 12.64